1. Technical Field
This invention relates in general to semiconductor memories, such as Dynamic Random Access Memories (DRAMs), and, more specifically, to devices and methods for supplying current to semiconductor memories from external sources to support boosted voltages, such as wordline voltages and isolation gate voltages, within such memories while they are tested.
2. State of the Art
Dynamic Random Access Memories (DRAMs) typically include various circuitry that will only operate properly when supplied with a voltage (denoted "V.sub.CCP ") that is "boosted" above the supply voltage (denoted "V.sub.cc "). Such circuitry includes, for example, wordlines, which require a boosted voltage V.sub.CCP to store a full V.sub.cc level in a memory cell, and isolation gates, which require a boosted voltage V.sub.CCP to pass a full V.sub.cc level along a digit line.
In order to supply the boosted voltage V.sub.CCP, DRAMs typically include an internal charge pump that generates the boosted voltage V.sub.CCP on one or more capacitors. These capacitors are typically relatively large so they can supply sufficient current I.sub.CCP to meet any demands that may be made on the charge pump by the DRAM circuitry.
During DRAM compression-mode testing, the demand for current I.sub.CCP from the charge pump may be many times the demand for current I.sub.CCP during normal memory operations. This is because many more wordlines and isolation gates may be operated at the same time during compression-mode testing than during normal memory operations.
Consequently, DRAM designers typically find it necessary to provide a DRAM with a charge pump having capacitors of sufficient size to meet the increased demand for current I.sub.CCP experienced during compression-mode testing, despite the fact that much smaller capacitors would suffice for normal memory operations. As a result, DRAMs shipped to customers typically include charge pumps with capacitors many times the size required for even the most rigorous field applications. These over-sized capacitors unnecessarily occupy integrated circuit (IC) die "real estate," and thus can either limit the functional circuitry that can be provided in a DRAM, or necessitate a larger die than is desirable for a DRAM.
Therefore, there is a need in the art for a device and method for providing current I.sub.CCP to a DRAM or other semiconductor memory during testing without having to use a charge pump with over-sized capacitors.